In general, pipe lines for transporting fluid there through are connected at given positions in the lines by the use of pipe fittings. In such case, elbows are used as the pipe fittings for changing the direction of the pipe lines.
Conventionally, because a solid core forged member is used as the elbow material, drilling works are necessary to form a fluid passage inside from both end surfaces to a center portion inside the member.
However, as the result of such drilling works from each end side to the center portion, there is a problem that a crossing portion is formed, in which fluid resistance becomes large in view of lack of smoothness of the fluid passage.
In addition, there is another problem that the manufacturing cost rises up because it is necessary to do cutting operation such as rough and finish drilling works for the fluid passage and to dispose the chip.
On the other hand, it is disclosed in the patent literature 1 that pipe members such as a rear stay of the motor cycle are bent by pressing, though the rear stay itself is different from the elbow mentioned above.
As shown in FIG. 3 of the patent literature 1, there is provided with a pair of dies turnably supported by a pair of support axes which are parallel each other. A pipe is mounted on them in the direction of crossing with the support axes. Both ends of the pipe are held tight between a stopper mounted on the one die and a press cylinder mounted on the other die. It is characterized in that a punch is pushed down onto the pipe portion between the dies, while exerting compression forces in the longitudinal direction to the pipe by means of the cylinder.
In addition, as a solution to the above disadvantages, a method and an apparatus for manufacturing elbow material having a thick walled bent pipe described in the patent literature 2 is proposed.
In the patent literature 2, as the prior art the apparatus includes an upper die 210 having a presser die 212 and an upper guide 211 having a guide surface 211a in a circular arc form for guiding a pair of lower dies 221 and 222, as shown in FIG. 10. The apparatus also includes a pair of lower dies 221 and 222 having sliding plane 220c and 220c in a circular arc form, and a lower guide 230 having sliding planes 230a and 230a for mounting a pair of the lower dies 221 and 222 thereon. In connection with a descent of the upper die 210, the sliding planes 220c and 220c in the circular arc form of a pair of lower dies 221 and 222 abut to and slide along the guide surface 211a in the circular arc form of the upper guide 211 of the upper die 210. At the same time as this, lower end portions 220f and 220f of a pair of the lower dies 221 and 221 abut to and slide along the sliding planes 230a and 230a of the lower guide 230. Sliding in this manner makes the structure in which a pair of the blower dies 221 and 222 are respectively rotatable opposite to each other.
According to this apparatus, a pair of the lower dies 221 and 222 rotates along the guide surface 211a in the circular arc form of the upper die 210, having a center of rotation O1 while they are facing to each other. Thereby, changes in the distances between both the end surfaces of the thick-walled pipe material 111a and the center O1 of rotation at the start of bending and at the completion of bending are reduced, thus making it possible to form a thick walled elbow material that is a thick-walled bent pipe with less variation in size.
As a result, the thick walled pipe can be cut and used as an elbow material, thus making it unnecessary to prepare a forged material. Further, since a thick walled pipe can be used, drilling for making slender holes to form fluid passages is unnecessary. Further, deburring at the crossing portion of the drilled holes, which is conventionally performed, is made unnecessary.
Furthermore, since the thick walled pipe is round in the outer shape, the margin to cut for screw thread cutting is reduced. Accordingly, a special drill is not needed, drilling work and deburring work are not needed, and cutting amount for screw threading work is reduced, whereby the time required for work, and tool cost can be substantially reduced, and the yield of the material can be improved.
However, since the upper guide 211 of this apparatus has the guide surface 211a in the circular arc form, the guide surface 211a in the circular arc form has to be worked by cutting a block to produce the upper guide 211, which requires a large amount of work and makes the work complicated, and as a result, work cost becomes high. Since the upper guide 211 is in a block form, it has heavy weight, which is inconvenient in handling. Further, the sliding surfaces 220c and 220c in the circular arc form of a pair of the lower dies 221 and 222 abut to and slide along the guide surfaces 211a in the circular arc form of the upper guide 211 of the upper die 210, and thus the sliding surfaces 220c and 220c and the guide surfaces 211a in the circular form are worn or seized if they are used for a long period of time.
In order to solve such problems, as shown in FIGS. 1 to 8 of the patent literature 2 discloses an apparatus for manufacturing a thick walled bent pipe comprising: a presser die; a lower die movably attached to a stationary portion of the apparatus, the lower die including a pair of bottom dies having means for meshing with means to be meshed which is secured to the stationary portion of the apparatus and biasing means for pressing the pair of bottom dies upward by a resilient force such as a spring force or the like; wherein, at the time of formation, the pair of the bottom dies are caused to rotate opposite to each other about a single center point from an initial position as the means for meshing meshes with the means to be meshed, with a descent of the presser die to perform the formation and, after the formation is finished, the pair of bottom dies are pressed upward by the biasing means and caused to rotate opposite to each other about the single center point as the means for meshing meshes with the means to be meshed, with an ascent of said pressure die, to thereby return to the initial position.
Also, the Patent literature 2 discloses a method for manufacturing a thick walled bent pipe using the apparatus, comprising the steps of placing a thick walled metal pipe material of a predetermined length on a lower die comprising a pair of bottom dies moveably attached to a stationary portion of a bending apparatus, said pair of bottom dies having means for meshing with means to be meshed that is secured to said stationary portion of said bending apparatus; pressing a middle portion in a longitudinal direction of said thick walled metal pipe material by lowering a presser die, and thereby rotating the pair of said bottom dies opposite to each other about a single center point from an initial position as the means for meshing meshes with the means to be meshed, to form a thick-walled elbow material of a predetermine size; and after the formation is finished, pressing the pair of bottom dies upward by biasing means to cause the pair of bottom dies to rotate opposite to each other about the single center point as the means for meshing meshes with the means to be meshed, to thereby return the pair of bottom dies to the initial position.    Patent literature 1: Official gazette of Japanese patent published (unexamined) No. 50-102562    Patent literature 2: Official gazette of Japanese patent No. 3544183Problem to be Solved by the Invention
There are following disadvantages in case that the apparatus disclosed in the patent literature 1 is applied to manufacture the elbow material.
Namely, in the patent literature 1, it is necessary to substantially increase rigidity of the support axes 5, 6 because the force necessary to push down the punch 10 onto the pipe portion becomes much more than the rear tray in bending formation of the elbow material from the pipe 9 with relatively thick walled metal pipe under the room temperature.
In addition, the bending stress is concentrated in the central portion of the curvature radius R because the central portion of the pipe 9 is directly pushed down by means of the lower end side of the punch 10. Accordingly, it is difficult to easily define the pushing pressure value that requires various experimental tests while taking into account of the sectional shapes and quality of the material of the pipe.
On the other hand, in the patent literature 2 there are provided with the linear racks 35a having the guide surfaces 31a, 31a of a pair of guide blocks 31, 31 and the fan like circular arc racks 25a, 25a meshing with the linear racks, which are formed on the bottom dies 21, 22.
Accordingly, geometrically in accordance with the downward movement of the presser die 12, the point of intersection OE1, namely, the bending center of the pipe material 111a, corresponding to the point O1 in FIG. 3 of the patent literature 2, exists on the vertical center line X along which the presser die 12 moves upward and downward.
However, there is a disadvantage that holding the center O1 on the vertical center line X constantly does not be guaranteed in the long time, because the constant holding depends on the machining accuracy and the mounting state of the linear racks 35a, the arc racks 25a, and the dust invasion into the meshing portions, and further because the position of the rolling surface 20C changes radially due to the forces acting radially on the tooth plane in mesh, as described in the paragraph 0040 that the circular rolling surfaces 20C, 20C roll on the guide surfaces 31a, 31a and are forced by a pair of the lower dies 21, 22, respectively.
In addition, in the patent literature 2, it is stated that the facing distance between the first and second stoppers 51, 52 limiting the end surfaces of the pipe material mounted thereon can be adjusted by the screw on the position of the one stopper. However, there is another disadvantage that the pipe material is not mounted on the lower dies in correct when the pipe material has error in its dimension because the adjustable range is relatively small, and also the screw should be rotated clockwise and counter clockwise corresponding to fastening and loosing at each forming operation.
Further, as shown in FIGS. 5, 8 of the patent literature 2, because the lateral face die 61 is forced upward by the spring 68 in full time there is a dangerous possibility that the bent pipe material at high temperature moves upward while attaching to the presser die 12 and on the way falls down in the vicinity of the forming apparatus, when the presser die 12 moves upward after the forming is completed.
The present invention is proposed to solve the problems mentioned above.
The object of the present invention is to provide an elbow material, and a production device and a production method thereof, wherein the elbow material is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member.
According to the production device and the production method of the present invention, there is no shift of the center point of bending of the metal hollow thick walled member. In addition, the bent and formed metal hollow thick walled member is not detached from the lower dies when an upper presser die moves upward, and a pair of parallel surfaces can be formed on the member for engaging a spanner.
Means for Solving the Problem
In order to achieve the object the elbow material is so constituted that it is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member.
In the case, the peripheral sectional shape of the metal hollow thick walled member can be the tetragon, the hexagon or the octagon, preferably the regular tetragon, the regular hexagon or the regular octagon.
Furthermore, in order to achieve the object the elbow material production device according to the present invention is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member and so constituted that comprises                a toggle type link mechanism formed by a first guide member movably guiding a first axial member for a supporting point to a first direction perpendicular to the axial direction of the first axial member, a pair of link levers, each being pivotally connected to the first axial member at one end portion of the link lever, and a second guide member movably guiding the other end portion of the link lever to a second direction perpendicular to the axial direction of the first axial member,        two half dies constituting one side (lower side) die arrangement formed so as to contact one side outer surface corresponding to approximately a half surface region in the longitudinal direction of the metal hollow thick walled member to be formed,        an one side die arrangement holding member for fixedly holding each of the half die, each member being fixedly connected to the lateral surface of the link lever,        an other side (upper side) die arrangement having a first contact surface and a second contact surface, the first contact surface contacting the other side outer surface of the metal hollow thick walled member in the state bent to a predetermined angle, and the second contact surface formed in the central portion contacting an outer surface portion of the first axial member so as to press the first axial member in the first direction,        an other die arrangement holding member for fixedly holding the other side die arrangement,        a first moving means for moving the other die arrangement holding member in the first direction,        a second moving means for moving the first axial member in the first direction along the first guide member through contacting the one end portion of the link lever pivotally connected to the first axial member.        
In the case, the elbow material production device can be provided with a stopper member which contacts the outer surface of the one side die arrangement holding member, the stopper member being located corresponding to the position of the first axial member at which the metal hollow thick walled member is bent to the predetermined angle.
Also, in the case, one side (lower side) die arrangement including the two half dies can be provided with a position limiting means for limiting the end side positions of the metal hollow thick walled member.
Also, in the case, at least one of the positions limiting means can be provided with a member with the position adjustable which contacts the end side of the metal hollow thick walled member.
Further, in the case, the first axial member can be constituted to be able to advance and retract in the axial direction in accordance with the movement in the first direction, and the end side of the first axial member can be constituted to contact and press the lateral surface of the metal hollow thick walled member.
Further, in the case, the end side of the first axial member can be constituted to contact the pair of parallel surfaces of the metal hollow thick walled member and hold the contact positions of one end surface in the axial direction of the first axial member.
Also, the toggle type link mechanism formed by the first guide member movably guiding the first axial member for the supporting point to the first direction perpendicular to the axial direction of the first axial member, the pair of link levers, each being pivotally connected to the first axial member at the one end portion of the link lever and the second guide member movably guiding the other end portion of the link lever to the second direction perpendicular to the axial direction of the first axial member,                the two half dies constituting the one side (lower side) die arrangement formed so as to contact with the one side outer surface corresponding to approximately a half surface region in the longitudinal direction of the metal hollow thick walled member to be formed,            and the one side die arrangement holding member for fixedly holding each of the half die, each being fixedly connected to the lateral surface of the link lever, can be constituted to put in a space surrounded by side wall plates (54, 56) and outer side wall plates (50,52) mounted on a base plate (16)
Also, in order to achieve the object the elbow material production method according to the present invention, which is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member, is constituted to include the steps of
preparing a bending apparatus which comprises    a toggle type link mechanism formed by a first guide member movably guiding a first axial member for a supporting point to a first direction perpendicular to the axial direction of the first axial member, a pair of link levers, each being pivotally connected to the first axial member at one end portion of the link lever and a second guide member movably guiding the other end portion of the link lever to a second direction perpendicular to the axial direction of the first axial member,    two half dies constituting one side (lower side) die arrangement formed so as to contact with one side outer surface corresponding to approximately a half surface region in the longitudinal direction of the metal hollow thick walled member to be formed,    an one side die arrangement holding member for fixedly holding each of the half die, each being fixedly connected to the lateral surface of the link lever, an other side (upper side) die arrangement having a first contact surface and a second contact surface, the first contact surface contacting the other side outer surface of the metal hollow thick walled member in the state bent to a predetermined angle, and the second contact surface formed in the central portion contacting an outer surface portion of the first axial member so as to press the first axial member in the first direction,    an other side die arrangement holding member for fixedly holding the other side die arrangement,    a first moving means for moving the other side die arrangement holding member in the first direction,    a second moving means for moving the first axial member in the first direction along the first guide member through contacting the one end portion of the link lever pivotally connected to the first axial member,            a first process for arranging the two half dies on the same line through driving the second moving means,        a second process for locating the metal hollow thick walled member heated in advance to the temperature capable of plastic deformation to the predetermined position of the half dies after the first process,        a third process for contacting the second contact surface formed in the other side die arrangement to the outer surface portion of the first axial member through driving the first moving means and moving the holding member of the other side die arrangement to the metal hollow thick walled member,        a fourth process for moving the first axial member with a first pressing force in the first direction through further driving the first driving means after the third process and causing the two half dies to depart from and slope each other in accordance with the moving, and as the result bending little by little the metal hollow thick walled member,        a fifth process for allowing the first axial member to move in the first direction while in the fourth process the second moving means forces a second pressing force through the one end portion of the link lever to the first axial member, the second pressing force being smaller than the first pressing force and with the direction opposite to the first pressing force which is supplied to the first axial member through driving the first moving means,        a sixth process for holding the other side die arrangement at a predetermined position in the first direction during a predetermined time interval using the first moving means, the predetermined position corresponding to the state in which the metal hollow thick walled member is bent to a predetermined angle through moving the first axial member in the first direction and contacting the other side die arrangement to the outer surface of the metal hollow thick walled member during the fourth process,        a seventh process for departing the other side die arrangement from the metal hollow thick walled member bent to the predetermined angle through moving the other side die arrangement holding member in the direction opposite to the direction in the third process by means of the first moving means after the sixth process,        a eighth process for returning the first axial member in the first direction so that the two half dies mounting the metal hollow thick walled member bent to the predetermined angle are arranged on the same line as the initial state through driving the second moving means after starting the seventh process.        
In the case since the bending apparatus is provided with the stopper member which contacts the outer surface of the one side die arrangement holding member and locates corresponding to the position of the first axial member at which the metal hollow thick walled member has been bent to the predetermined angle, the stopper member can receive the first pressing force acting on the first axial member during the sixth process.
Also, in the case the half die can be provided with a position limiting means for limiting the end side positions of the metal hollow thick walled member.
Also, in the case at least one of the position limiting means can be provided with a member with the position adjustable which contacts the end side of the metal hollow thick walled member.
Further, in the case the first axial member can be constituted to be able to advance and retract in the axial direction in accordance with the movement in the first direction during the fourth process, and the end side of the first axial member can be constituted to contact and press the lateral surface of the metal hollow thick walled member.
Further, in the case the end side of the first axial member can be constituted to contact the pair of parallel surfaces of the metal hollow thick walled member and hold the contact positions in the axial direction during the fourth process.
Effect of the Invention
Since the elbow material with the polygonal periphery according to the present invention is formed in advance as the metal hollow thick walled member before it is bent to form the elbow shape so that the elbow material has the hollow passage of an approximately circular section along the axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member, it is unnecessary to form a pair of parallel surfaces for the spanner engagement during bending formation.
Also, since the elbow material production device according to the present invention is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member and so constituted that it comprises                a toggle type link mechanism formed by a first guide member movably guiding a first axial member for a supporting point to a first direction perpendicular to the axial direction of the first axial member, a pair of link levers, each being pivotally connected to the first axial member at one end portion of the link lever and a second guide member movably guiding the other end portion of the link lever to a second direction perpendicular to the axial direction of the first axial member,        two half dies constituting one side (lower side) die arrangement formed so as to contact one side outer surface corresponding to approximately a half surface region in the longitudinal direction of the metal hollow thick walled member to be formed,        an one side die arrangement holding member for fixedly holding each of the half die, each member being fixedly connected to the lateral surface of the link lever,        an other side (upper side) die arrangement having a first contact surface and a second contact surface, the first contact surface contacting the other side outer surface of the metal hollow thick walled member in the state bent to a predetermined angle, and the second contact surface formed in the central portion contacting an outer surface portion of the first axial member so as to press the first axial member in the first direction,        an other die arrangement holding member for fixedly holding the other die arrangement,        a first moving means for moving the other die arrangement holding member in the first direction,        a second moving means for moving the first axial member in the first direction along the first guide member through contacting the one end portion of the link lever pivotally connected to the first axial member,        the elbow material production device is strongly built and solid as a bending apparatus for the elbow material and enables to use it for long term.        
Also, further since the elbow material production method according to the present invention, which is formed by bending to a predetermined angle a metal hollow thick walled member of a given length having a hollow passage of an approximately circular section along an axial direction of the member with both ends opened, and approximately circular or at least one pair of parallel surfaces in the periphery of the member, is constituted to include the steps of                preparing a bending apparatus which comprises            a toggle type link mechanism formed by a first guide member movably guiding a first axial member for a supporting point to a first direction perpendicular to the axial direction of the first axial member, a pair of link levers, each being pivotally connected to the first axial member at one end portion of the link lever and a second guide member movably guiding the other end portion of the link lever to a second direction perpendicular to the axial direction of the first axial member,    two half dies constituting one side (lower side) die arrangement formed so as to contact with one side outer surface corresponding to approximately a half surface region in the longitudinal direction of the metal hollow thick walled member to be formed,    an one side die arrangement holding member for fixedly holding each of the half die, each being fixedly connected to the lateral surface of the link lever, an other side (upper side) die arrangement having a first contact surface and a second contact surface, the first contact surface contacting the other side outer surface of the metal hollow thick walled member in the state bent to a predetermined angle, and the second contact surface formed in the central portion contacting an outer surface portion of the first axial member so as to press the first axial member in the first direction,    an other side die arrangement holding member for fixedly holding the other side die arrangement,    a first moving means for moving the other side die arrangement holding member in the first direction,    a second moving means for moving the first axial member in the first direction along the first guide member through contacting the one end portion of the link lever pivotally connected to the first axial member,            a first process for arranging the two half dies on the same line through driving the second moving means,        a second process for locating the metal hollow thick walled member heated in advance to the temperature capable of plastic deformation to the predetermined position of the half dies after the first process,        a third process for contacting the second contact surface formed in the other side die arrangement to the outer surface portion of the first axial member through driving the first moving means and moving the holding member of the other side die arrangement to the metal hollow thick walled member,        a fourth process for moving the first axial member with a first pressing force in the first direction through further driving the first driving means after the third process and causing the two half dies to depart from and slope each other in accordance with the moving, and as the result bending little by little the metal hollow thick walled member,        a fifth process for allowing the first axial member to move in the first direction while in the fourth process the second moving means forces a second pressing force through the one end portion of the link lever to the first axial member, the second pressing force being smaller than the first pressing force and with the direction opposite to the first pressing force which is supplied to the first axial member through driving the first moving means,        a sixth process for holding the other side die arrangement at a predetermined position in the first direction during a predetermined time interval using the first moving means, the predetermined position corresponding to the state in which the metal hollow thick walled member is bent to a predetermined angle through moving the first axial member in the first direction and contacting the other side die arrangement to the outer surface of the metal hollow thick walled member during the fourth process,        a seventh process for departing the other side die arrangement from the metal hollow thick walled member bent to the predetermined angle through moving the other side die arrangement holding member in the direction opposite to the direction in the third process by means of the first moving means after the sixth process,        a eighth process for returning the first axial member in the first direction so that the two half dies mounting the metal hollow thick walled member bent to the predetermined angle are arranged on the same line as the initial state through driving the second moving means after starting the seventh process,            the bending center position does not deviate in the metal hollow thick walled member, and in addition, the bent metal hollow thick walled member does not separate from the lower half dies in the one side die arrangement when the upper presser dies in the other side die arrangement moves upward.